Carriage of Oxygen

Question 1

What is oxidation?

Answer 1

Loss of electrons –> releases energy

Question 2

What is reduction?

Answer 2

Gain of electrons –> requires energy

Question 3

How is haemoglobin chemically adapted to carry oxygen?

Answer 3

Combines rapidly and reversibly without becoming oxidised

Question 4

Why is oxygen a difficult molecule to transport?

Answer 4

Powerful oxidising agent

Question 5

What are reticulocytes?

Answer 5

Immature red blood cells (just left bone marrow) - have mesh-like rRNA network

Question 6

Why do erythrocytes require ATP?

Answer 6

To maintain Na+ pumps in membrane, so they make ATP via glycolysis (glucose –> pyruvate)

Question 7

What is methaemoglobin?

Answer 7

Oxidised form of haemoglobin after much oxygen exposure (prior to breakdown) which cannot carry oxygen

Question 8

How many unpaired electrons does oxygen have?

Answer 8

4

Question 9

How many unpaired electrons does Fe2+ have?

Answer 9

6

Question 10

Describe the chemical structure of haemoglobin

Answer 10

Ferrous iron (Fe2+) is core molecule:
4 bonds go to nitrogen groups (covalent) with haem attached
1 bond goes to histidine amino acid below
1 bond is free to bind to oxygen

Question 11

What is steric hindrance?

Answer 11

3D folding of haemoglobin prevents oxygen molecule getting close enough to the ferrous iron to remove the spare electron (prevents oxidation –> reversible bond)

Question 12

Describe the molecular structure of haemoglobin

Answer 12

4 subunits (2 alpha, 2 beta) bound together by salt bridges, hydrogen bonds and hydrophobic interactions with prosthetic haem attached

Question 13

What happens to methaemoglobin?

Answer 13

May be converted back to functioning oxygen-carrying capacity by NADH-dependent methaemoglobin reductase (if newly formed) or broken down in liver/spleen

Question 14

Describe the structure of foetal haemoglobin

Answer 14

2 gamma subunits with higher affinity for oxygen than adult haemoglobin

Question 15

What may affect the ability of haemoglobin to bind to oxygen?

Answer 15

pH, partial pressure of CO2 etc

Question 16

Describe sickle cell disease

Answer 16

Defective form of haemoglobin formed (haemoglobin S) which has mutant beta subunits, causes RBCs to change shape to sickle-shaped which may stack and block blood vessels

Question 17

Describe thalassaemia

Answer 17

Inherited autosomal recessive blood disease which results in less/no globin chains which make up haemoglobin –> abnormal RBCs –> reduction of oxygen transport –> anaemia

Question 18

Describe the oxygen dissociation curve

Answer 18

S shaped

Question 19

How does temperature affect the oxygen dissociation curve?

Answer 19

High temp (metabolising tissue) - curve moves right to unload more oxygen at any given partial pressure
Low temp (slow metabolism) - curve may more left, so less oxygen is given up --> hypoxia and fatigue

Question 20

How does pH affect the oxygen dissociation curve?

Answer 20

Bohr shift - curve moves to the right with lower pH (more acidic from CO2 production) –> greater oxygen unload

Question 21

How does carbon monoxide affect the oxygen dissociation curve?

Answer 21

Greater affinity for haemoglobin than oxygen, forming carboxyhaemoglobin –> death by hypoxia may result

Question 22

What is myoglobin?

Answer 22

Form of haemoglobin found in muscle, it’s single subunit and has greater oxygen affinity than haemoglobin (so O2 is transferred in capillaries)

Question 23

What is rhabdomyolysis?

Answer 23

When myoglobin is released from damaged muscle tissue

Question 24

How may rhabdomyolysis cause acute renal failure?

Answer 24

Released myoglobin from muscle damage is filtered by kidney but is toxic to renal tube epithelia so can cause kidney failure

Question 25

What is haematocrit?

Answer 25

Percentage of blood that is red blood cells

Question 26

What controls red blood cell production?

Answer 26

Erythropoietin (EPO) produced by kidneys and liver.

If kidney is hypoxic –> EPO increased

Question 27

In what ways is carbon dioxide removed from respiring cells?

Answer 27

Diffuses into water/plasma, converted to bicarbonate (carbonic anhydrase) and carried in plasma, carboxyhaemoglobin (direct binding to haemoglobin)

Question 28

Which ion maintains electroneutrality with bicarbonate movement in and out of cells?

Answer 28

Chloride (Cl-)